1. Field of the Invention
This inventions relates to a roller switch. It particularly relates to a roller switch suitable for use in handheld electronic equipment such as portable radio telephones.
2. Description of the Prior Art
Portable radio telephones require a number of keys to enable the user to operate the phone. As well as the regular alphanumeric keys (0-9, *, #), additional function keys are necessary in order to access menus, adjust volume, or scroll up or down for instance. Scrolling up or down through a long list of possible options can be time consuming and awkward when individual key presses have to be used.
Possible alternative means of scrolling that have been suggested or implemented are the trackball, as used in a computer xe2x80x98mousexe2x80x99, or the roller switch 10, as used in the Nokia(copyright) 7110 mobile phone 1, as shown in FIG. 1. Trackballs tend to be difficult to implement in hand-held equipment, and are prone to malfunction due to ingress of dust and dirt, and so are not the preferred option at present. While offering only one-dimensional control and not two-dimensional control like the trackball, roller switches are found to offer satisfactory performance in portable telecommunication equipment. Indeed, they are found to offer several advantages over using individual up/down or left/right keys. For instance, entering text into a mobile phone using only the numeric keypad can be time-consuming and prone to error due to the grouping of several letters on each key (2=abc, 3=def, 4=ghi etc.) and the multiple key presses that are required to access any given letter. For instance, to enter the work xe2x80x98switchxe2x80x99, the following key presses are required: 7-7-7-7-9-4-4-4-8-2-2-2-4-4 i.e. fourteen individual key presses are needed to enter this six-letter word.
The use of a roller switch 10 can enable easier entry of characters. When the phone is in a text entering mode, an alphabetical list 11 is presented on the phone display, and the user can scroll up or down the list by rolling the roller switch 10 in an upward or downward direction respectively. This enables the user to scroll through all letters of the alphabet with one continuous action. To increase functionality further, the roller switch is additionally adapted to be depressed, with the depression triggering a further switch that can be used to indicate selection of a highlighted option on the display. In the example shown in FIG. 1, the letter xe2x80x9cjxe2x80x9d is highlighted, and depressing the roller switch 10 will select that letter and enter it into the text at the entry point defined by a cursor.
Such a roller switch is disclosed in co-assigned patent application EP0901262A. FIG. 2a shows a view of the roller switch assembly of this patent application, and FIG. 2b shows a view of the roller barrel and associated encoder parts in isolation.
FIG. 2a shows the roller barrel mounted for rotation in its support structure. It shows the hinge 28 which connects the assembly to the telephone. It is the structure of this point that allows the switch to be depressed, effectively rotating about the hinge 28, thus actuating a further micro switch positioned underneath the roller barrel assembly. Also shown is a terminal part 62 which carries the electrical contacts from the switch.
FIG. 2b shows an end view of barrel 60, and the encoder pattern 70 disposed thereon. The encoder pattern comprises conducting and non-conducting portions. The conducting portions are shown as the white areas. The non-conducting portions are the shaded areas. Also shown are the positions of the three sensors X, Y and Z which co-operate with the encoder to sense the rotation of the barrel 60.
The sensors them selves are arranged to be parallel with the end face of the barrel. The signals received by a microprocessor from each of the sensors will depend on whether it is currently contacting a conducting or non-conducting portion of the encoder pattern. From changes in these signals it is possible to determine whether the roller barrel is being rotated, and also in which direction rotation is occurring. A full description of this process can be found in EP0901262A.
However, a problem with such a switch arrangement occurs when the overall thickness of the telephone is reduced. Telephones are now feasible which have an overall thickness approximating, or even smaller than, the diameter of the roller switch shown in FIGS. 1 and 2. In order to provide suitable encoding structures, a certain barrel diameter is required. This can result in a roller switch which is disproportionately large compared to the rest of the telephone and, consequently, difficult to accommodate within the housing.
According to the present invention, there is provided a rotary switch comprising: a rotatable barrel, having an axis of rotation; and an encoder pattern for sensing rotation of the barrel wherein the encoder pattern extends in a longitudinal direction with respect to the axis of rotation of the barrel.
By positioning the encoder pattern such that it is longitudinal with respect to the axis of rotation of the roller barrel, it is possible to devote a greater surface area to the encoder pattern, thus allowing for greater reliability and accuracy in sensing the true position of the roller barrel, without needing to provide a large surface area at the end of the barrel. This allows the barrel diameter to be reduced.
The encoder pattern consists of one or more discrete bands. The band, or bands, do not need to be arranged to be coaxial with the axis of rotation of the barrel, but the arrangement is simplified if this is the case.
Adopting a roller switch structure as defined above allows the switch to have a smaller barrel diameter, which can be more easily incorporated into ever smaller portable telephones and other handheld equipment.
The sensors, which contact the encoder pattern, are biased inwards, towards the encoder pattern to ensure reliable electrical contact.
Advantageously, the encoder pattern is arranged to be cylindrical in shape.
The encoder pattern can be implemented in a number of ways. Advantageous embodiments employ sensors relying on electrical contact with either conducting or non-conducting regions of the encoder pattern; or sensors responsive to magnetic and non-magnetic regions of the encoder pattern; or sensors responsive to light and dark regions of the encoder pattern.
The rotary switch of the invention enjoys particularly advantageous use in handheld electronic apparatus, where size can be an important design factor.
A particular use for the rotary switch may be found in portable radio telephones, including such wireless devices which offer data facilities, such as wireless access to the World Wide Web (WWW).
For a better understanding of the present invention, and to understand how the same may be brought into effect, the invention will now be described, by way of example only, with reference to the appended drawings in which: